Process for the regular obtaining of metals and more particularly of steel with determined characteristics



Patented July 20, 1937 UNITED STATES PATENT oF-nce PROCESS FOR THE REGULAR OBTAINING OF METALS AND MORE PARTICULARLY OF STEEL WITH DETEBDIINED CHARACTER- ISTICS No Drawing. Application July 2, 1935, Serial No. 29,506. In France May 2'1, 1935 9 Claims.

ments ordinarily determined apart .from the basis metal, that is to say for steel, carbon, silicon, manganese, phosphorus, sulphur and the addition metals, exhibit in use properties often very difierent. very great differences in properties in pieces made of such metals and brought into condition for use, in regard to mechanical characteristics, physical properties notably adaptability to quenching and to cementation, which properties are often taken as quality factors for a determined metal.

It is now admitted that such a set of properties is strongly influenced by the grain size of the metal and in particular that it bears a close relationship with the results which are obtained by subjecting the metal to the test instituted by MacQuaid and which is defined for example by the conditions fixed by the Standard E. 19-33 of the American Society for Testing Materials.

The grain size observed according to this test upon the metal which is called in the technical literature of the United States, MacQuaid grain size will be so called hereinafter.

It is known in particular, only to give one example, that a steel with 0.8% of carbon, 0.250% of manganese, 0.250% of silicon having a Mac- Quaid grain size of 3 to 5 exhibits when it is quenched at 780 C. in water a hardening penetration considerably greater than a steel of identical analysis having a MacQuaid grain size of 6 to 7 and possesses from this fact in use quite difierent properties. v

The possibility of producing with a metal of given analysis a MacQuaid grain size chosen in advance permits on the one hand, by producing systematically and regularly a metal with a predetermined MacQuaid grain size, a regularity to be ensuredin the properties of use which is quite essential; on the other hand it gives the possibility with a metal oithe same analysis, of obtaining at will within certain practical limits various characteristics of hardnesaof ductility, or others,

One may in particular meet with such by causing the MacQuaid grain size in this metal to vary.

Up to the present one has been working in the dark and in spite of the working conditions employed there has never been any certainty of obtaining the properties sought; upon different heats of a metal of the same analysis and even on the same heat, metals having very different MacQuaid grain sizes were obtained and consequently dissimilar properties and it was necessary to make, after solidification of the ingots, physical tests which served to classify into different categories the metals obtained. Having in view a definite MacQuaid grain size it happened very frequently that this grain size was not obtained for any of the ingots which fact did not permit them. to be used for the purpose in view. Very often steels were even obtained with extremely mixed grain sizes which was even more unfavourable.

Also the fact of being able to produce systematically and regularly for each heat in the manufacture of a metal, the MacQuaid grain sizes which are desired or which are specifically demanded by the customers and not other sizes is industrially of leading importance.

No explanation based upon scientific bases and verified experimentally has yet been proposed to explain thedifferences of MacQuaid grain sizes observed with steels of the same analysis. Different hypotheses have been put'forward, notably that based upon the formation of visible inclusions, but one after another they have had to be abandoned. The present tendency is to attribute a preponderating importance to the presence of extremely small refractory particles,

escaping miscroscopic observation, and especially to the nature of these invisibleuparticles and to their state of dispersion in the metal, but this still is only a hypothesis which has moreover the regular obtaining of the MacQuaid grain size .desired beforehand.

It is only known in practice at the present time that common addition elements of the metal, particularly of steels, can have from this point of view a very different influence upon the Mac- Quaid grain size and that certain of them such for example as aluminium and vanadium have a preponderating action upon the .MacQuaid grain size obtained, but the action of these elements does not appear to be solely the cause, and it is known that the same addition of the same element or of several el-ementsalways thesame, made from one operation to another, even under identical conditions, to metals of the same chemical analysis, frequently lead to very different MacQuaid grain sizes.

Also the metallurgical processes known at present have not yet permitted the systematic and in advance.

regular obtaining of MacQuaid grain sizes chosen This is particularly true in non- A alloyed carbon steel s--called in the United States plain carbon steels--and for the systematic production of intermediary and unmixed Mac- Quaid grain sizes (for example size 3 to 5 of the standard cited above) the production of which has been and is still extremely diflicult and has an extraordinarily small yield, and remains, one might say, to a very large extent left to chance.

The present invention brings the practical solution of this problem in the sense that it allows to be obtained regularly for each quality of metal, particularly of steel, predetermined Mac;v

Quaid grain sizes compatible with the analysis of the metal, as well as the characteristics of strength and ductility which are proposed, amongst others which the metal can furnish. These results are obtained according to the invention by subjecting the metal to a series of operations comprising:

(a) The addition to the metal, whatever its degree of oxidation, of the same quantity, predetermined for each case and above 0.050%, of one or more reducing substances currently called deoxidizing substances such for example as manganese or silicon and manganese, in the form of the simple substances or of simple or complex alloys, in the solid or liquid state. There may be performed one or more operations of addition of deoxidizing substances during the process. An operation of addition comprises the addition to the metal either of a single and the same deoxidizing substance or several deoxidizing substances added separately or simultaneously. The

- ing the ones above set forth as regards the naeration, the time necessary for the deoxidizing substances to be diflused in the bath. This pause in general varies with the carbon content of the steel, being shorter for a low carbon content. Under a weakly oxidizing slag or when manganese is added as the sole deoxidizing substance under the slag previously formed in the steelmaking operation, the'pause may be longer but in each case it should approach as closely as possible a duration fixed in advance.

(0) The separation of the metal from the initial slag which lies above it. This elimination is carried out either by slagging off from the furnacecontaining the metal or by retaining the slag in the furnace at the moment of pouring, or by pouring metal and slag into an intermediary ladle or receptacle and then pouring the metal from the bottom of this ladle.

(d) Putting into contact, by any operative method, the metal thus separated from its previous slag and which in the case of the previous addition of deoxidizing substances should con-- tain still relatively considerable quantities of these substances, with a synthetic molten basic,

acid or neutral slag composed principally of oxthe preceding operations and so that the slag rapidly covers the metal either by pouring the metal into the slag in the ordinary conditions of current practice of the pouring of metals, or with a violence such that the slag is finely subdivided by the impact of the metal, and is disseminated in the mass of metal set into violent turbulent movement by its kinetic energy, or by placing the synthetic slag in a furnace into which the metal is introduced, or by introducing it into the same furnace where the previous operation has been carried out.

If absolutely necessary the elements of this slag maybe added in the solid state, preferably heated in advance, provided that the proportion of these in the slag is such as to give a slag rapidly and readily fluid, but this is not recommended.

In any case the synthetic slag should accompany the metal up to the pouring into ingot mould.

(e) Addition to. the steel after its placing in contact with the molten synthetic slag of a quantity, fixed in advance, of a substance the action of which upon the MacQuaid grain size is especially energetic, such for example as vanadium, titanium, and most especially aluminium. This addition is made by adding these bodies either in the pure state or in the state of alloys containing one or more of these elements in known quantity, and possibly other elements such for ex- I ample as manganese, silicon, iron, in quantity fixed in advance.

The addition of the substances in question should be made at a moment as near as possible to the solidification of the steel in the ingot mould; it may be made in the furnaoeif a furnace is used or in a pouringladle but even better in the ingot moulds. The steel resting under the synthetic slag is poured in the usual manner. It is to be recommended to pour in conditions always as similar as possible for ingots of determined weight and relative dimensions.

For. each quality of metal for example steel, once an operative method in a determined furnace is chosen and well defined, the nature and the quantity of the additions of deoxidizing substances, the duration of waiting for the action of these deoxidizing substances, if there is a pause, the method of elimination of the previous slag, the nature and the quantity of synthetic slag put into operation beingthemselves well determined, there is added after contact with this synthetic slag a predetermined quantity of special substance acting upon the MacQuaid grain size for the sizes of grain sought, of aluminium for example.

This quantity of substance, the value of which will be chosen in advance for obtaining the desired grain sizes may be extremely small, and even in the limiting case be zero, in the particular case where relatively large grains are sought and provided that the additions of deoxidizing substances have been made in sufficient quantity, for example an addition of about 0.300% of silicon according to the figures predetermined and fixed in advance.

Experiment proves that by operating in the conditions described above the following very remarkable result is obtained.

By making always under the same conditions the same deoxidizing additions, silicon and man ganese for example, or substantially the samefor one may, without this being recommended, allow if necessary a certain variation in the quantity of manganese and even in that of silicon the same addition of elements having a strong action upon the MacQuaid grain siz for example aluminium, gives in a regula manner practically always the same MacQuaid grain sizes for a metal of a given analysis.

In other terms one may say that due to the invention the action of elements which have a preponderating effect upon the MacQuaid grain size, which action is not constant in the old processes, is stabilized and rendered regularly constant, by previous and well defined action of deoxidizing substances and a synthetic slag.

The operative method which seems at present most to be recommended consists in separating the metal from its initial slag by any known efficacious means and by pouring it violently upon the molten synthetic slag rendered very fluid and placed in a ladle, the violence of pouring being such that the slag is divided by the impact of the metal and entrained and dispersed in the interior of the said mass of metal, itself set into violent turbulent movement by the violence of the pouring, according: to the processes described in the Perrin United States Patent No. 2,015,691 of Ootober 1, 1935.

The addition of the deoxidizin'g'substances is made before or during the intermixing or partly before and partly afterwards according to the indications furnished above, and preferably addition in the ingot mould is adopted as the method of addition of the elements acting strongly upon the grain size. 0 v

The operation of intense intermixing of the metal and of the slag favouring the obtaining of a state near equilibrium between the slag and the metal, any subsequent action of the slag upon the metal is practically suppressed.

Experiment proves that in such an operative method with the same or substantially the same deoxidizing additions, there is obtained an even more remarkable regularity of the MacQuaid grain size, during the whole of a heat and from one heat to another, of a metal of the same analysis even for MacQuaid grain sizes of 3 to 5 for carbon steels, grain sizes the extreme difliculty of production of which is well known.

One has thus, due to the complete automaticity of the process based solely upon chemical equilibria produced in an extremely short time and protected from disturbing factors, a remarkable solution of the problem of leading importance of the control of the MacQuaid grain size, obviously within the limits of the possibilities resulting from the analysis of the metal and this without it being necessary to take at any moment of the whole of the process any test portion of the fused metal, otherwise than for the control of the temperature and of the current chemical characteristics.

\ A previous adjustment of all the conditions will be made for each analysis of the metal and for each quality of the metal required, according to the importance of the additions of alloys which were made. v

For example in as far as concerns the addition of elements acting strongly uponthe MacQuaid grain size, for example aluminium, and concerning in particular a heat of determinedanalysis, to obtain a MacQuaid grain size of 3 to 5 with an addition of 0.250% of silicon and 0.300% of manganese, the quantity of aluminium to be added will be determined by the following process.

Upon the bare bath a few minutes before intermixing with the synthetic slag,an addition of Si and Mn of the order of the quantities required by the customers in the steel in view is made, while slightly increasing these quantities; one will for example have added 0.300% of Si and 0.600% of Mn. The metal is intermixed violently with the synthetic slag and poured with the following successive additions of Al.

Percent 1 0.002 2 0.005

The test of the grain size is made and it is found that the sizes of 3 to 5 are obtained for example with a 0.010% of Al. The operation is then carried out according to the present invention for all the rest of the manufacture of the steel ordered or to be put into stock, with the MacQuaid grain sizes considered. This grain size will then be obtained with great regularity.

It is thus possible to define for each quality of steel a standard operative method which permits the absolutely regular obtaining of the MacQuaid grain size required in advance, and the mechanical characteristics of the steel.

Several examples of carrying out the process forming the subject of the invention will now be described comprising the addition of deoxidizing. substances made in a furnace upon oxidized steel and of subsequent additions of aluminium in ingot moulds which give, with a standardized operation in a furnace, comprising the slagging off of the basic slag before the additions of deoxidizing substances, the addition of these deoxidizing substances, the violent pouring of the steel (15 metric tons) on about 2 metric tons of a molten fluid slag with %of silica, and about 0.7% ,of FeO, the rest being composed of alumina, magnesia, lime, titanic acid,-the results of the.

MacQuaid grain size mentioned above in an absolutely constant manner by pouring always under the same conditions, heated ingots of 500 kgs. for the steels produced with this furnace. The number of combinations of different grades of steel being infinite only four examples have been given.

1. Carbon steel.C=0.35% without alloying elements. Addition of deoxidizing substances:

Mn=1% Si =0.250%

Grain obtained:

with 0.002% of aluminiumgrain a to 5; with 0.015% of Al-grain' 5 to 6.

2. Mild nickel chrome steel C =0.10% Ni=2.75% Cr=0.8%

Addition of deoxidizing substances:

Mm -0.500% si =0.300 I Grain obtained:

with 0.004% of Al-grain 3 to 5; with 0.025% of Algrain 5 to 6.

3. Chrome molybdenum steel Addition of deoxidizing substances:

Mn=1.200% Si =0.-17 5% Grain obtained:

with 0.006% oi'Al-grain 3 with 0.050% of Al-grain 6 4. Mild nickel steel Addition of deoxidizing substances:

' Mn=0.65% si =025% Grain obtained:

with 0.002% of Al-grain 3 to with 0.050%. of Al-grain '7 to 8.

All the elements and the combination of these elements having an importance upon the quantity of Al to be added for the obtaining of a determined grain--an influence often different according as to whether it concerns intermediary grains and fine grains-it can only be given in examples, the precise adjustment having to be made in each particular case, but this is extremely easy to efiect by a few tests once the method, is generally a breaking load of about 65 kgs., an elongation of about 12 and a .Mesnager resiliency of about 25.

With an addition of 0.050% .Al the breaking load ialls to about 55 while the elongation and the Mesnager resiliency rise respectively to about 18 and 3'1.

With intermediate additions the flgurm ob'- 4 ductility which it is desired to obtain, and obtain them very regularly by making ones choice according to the use for which the metal is intended.

In the same way with nickel chrome cemented steels of the same analysis, one may thus predetermine the conditions for obtaining according to requirements and the appl oil quenching from 850 C., tween 105 and 125 kgs One may thus by the present process have control of the mechanical characteristics of the steel which is made and reproduce them at will in very good conditions of approximation, instead of doing what one doesfrom habit, that is to say establish them once the heat is made and determine from them the use to which the metal will be put.

What I claim is: 1. The process of controlling the grain size of steel which comprises the steps of forming a bath of molten steel covered with slag, Separating the metal from the slag, then adding to the molten steel a deoxidizlng agent of theclass consisting of silicon and manganese and quickly protecting the molten steel with a synthetic slag of predetermined composition and quantity and composed principally of oxides with a very high heat of formation and poor in iron oxide, and then casting the steel while protected bythe synthetic slag and adding to the molten steel a predetermined and suflicient amount of theclass consisting of aluminum, titanium and vanadium to produce the desired grain size.

2. The process of controllingthe grain size of steel which comprises the steps of forming a bath of molten steel covered with slag, separating the metal from the slag, then adding to the molten steel a deoxidizing agent of the class consisting of silicon and manganese, quickly inter-mixing the molten steel with termined composition and quantity and composed principallyof oxides with a very high heat of formation and poor in iron oxide so as to produce an intermixture of metal and finely divided slag and allowing the slag to separate from the metal and protect it against the action of the surrounding atmosphere, and then casting the steel while protected by the synthetic slag and adding to the molten steel a predetermined and suflicient amount of a metal of the class consisting of aluminum, titanium and vanadium to produce the desired grain size.

3. The process of controlling the grain size of breaking loads besteel which comprises the steps of forming a bath of molten steel covered with slag, separating the metal from the slag and adding a deoxidizing the grain size to'produce the desired grain size.

4. The process of controlling the grain size of steel which comprises the steps of forming a bath ication in view, alter asynthetic slag oi predeof a=metal agent and covering the molten steel after its of molten steelcovered with slag, separating the metal from the slag, .then adding a deoxldizing aoe'mso agent and covering the molten steel with a protecting synthetic slag of predetermined composition and quantity, and then casting the steel while protected ,by the synthetic slag and adding to the molten steel a predetermined and sum "cient amount of a metal having a strong action size.

upon the grain size to produce the desired grain 5. The process of controlling the grain size 01 steel which comprises the steps 01 forming a bath of molten steel covered with slag, separating the metal from the slag and adding a deoxidizlng agent, then quickly intermixing the molten steel with a synthetic slag of predetermined composition and quantity so as to form an intimate intermixture of metal and finely divided slag and allowing the slag to separate from the metal and protect it against the action of the surrounding atmosphere, and then casting the steel while protected by the synthetic slag and adding to the .molten steel a predetermined and sufllcient amount of a metal having a strong action upon the grain size to produce the desired grain size. 6. The process of controlling the grain size of steel which comprises the steps of forming a bath of molten steel covered with slag, separating the metal from the slag and adding a deoxidizing agent of'the class consisting of silicon and manganese and covering the molten steel alter its separation from the first slag with a protecting synthetic slag of predetermined composition and quantity, and then casting the steel while protected by the synthetic slag and adding to the molten steel a predetermined and sumcient amount of a metal of the class consisting of aluminum, titanium and vanadium to produce the desired grain size.

7. The process of controlling the grain size of steel which comprises the steps of forming a bath of molten steel covered with slag, separating the metal from the slag and adding to the bath a deoxidizing agent of the class consisting of silicon and manganese and covering the molten steel after its separation from the first slag with a protecting synthetic slag of predetermined composition and quantity, and then casting the steel while protected by the synthetic slag and adding to the molten steel a predetermined and suificient amount or aluminum to produce the desired grain size.

8. .The process of controlling the grain size of steel which comprises the steps of forming a bath of molten steel covered with slag, separating the steel and slag and pouring the molten steel into a molten synthetic slag of predetermined composition and quantity and adding a deoxidizing agent to the steel, and then casting the steel while protected by the synthetic slag and adding to the molten steel a predetermined and sufiicient amount of a metal having a strong action upon the grain size to produce the desired grain size.

9. The process of controlling the grain size of 3 steel which comprises the steps of forming a bath of molten steel covered with slag, separating the steel and slag and pouring the molten steel into a molten synthetic slag of predetermined composition and quantity and adding to the, steel a deoxidizing agent oithe class consisting of silicon and manganese, and then casting the steel while protected by the synthetic slag and adding to the molten steel a predetermined and sufiicient amount of a metal oi! the class consisting of aluminum, titanium and vanadium to produce 3 the desired grain size.

' RENE: PERRIN. 

